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Sat, 31 Oct 2026 02:08:24 -0700 (PDT) Received: from EAIT-H54D9Q2FJQ.eait.uq.edu.au ([130.102.10.191]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cdb09610f48sm1614184a12.2.2026.10.31.02.08.16 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 31 Oct 2026 02:08:23 -0700 (PDT) From: Yu Zhang To: Bjorn Andersson , Mathieu Poirier Cc: linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2] rpmsg: char: take ept_lock in the SET_INCOMING_FLOWCONTROL ioctl Date: Sat, 31 Oct 2026 19:06:50 +1000 Message-ID: <20261031090650.23701-1-yuz08559@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261026100306.68019-1-yuz08559@gmail.com> References: <20261026100306.68019-1-yuz08559@gmail.com> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rpmsg_eptdev_ioctl() handles RPMSG_SET_INCOMING_FLOWCONTROL by calling rpmsg_set_flow_control(eptdev->ept, ...) without holding eptdev->ept_lock and without checking eptdev->ept for NULL. rpmsg_set_flow_control() dereferences ept->ops, so this is the only eptdev->ept user that does not honour the ept_lock discipline. eptdev->ept is torn down under ept_lock: rpmsg_chrdev_eptdev_destroy() (reached via RPMSG_DESTROY_EPT_IOCTL on a second fd, or when the rpmsg device is removed) and rpmsg_eptdev_release() both do mutex_lock(&eptdev->ept_lock); rpmsg_destroy_ept(eptdev->ept); eptdev->ept = NULL; mutex_unlock(&eptdev->ept_lock); and rpmsg_destroy_ept() drops the endpoint's last reference and frees it. A SET_INCOMING_FLOWCONTROL ioctl running concurrently can therefore read eptdev->ept just as it is freed and dereference ept->ops -> use-after-free (or a NULL dereference once ept has been cleared). Fixes: 5550201c0fe2 ("rpmsg: char: Add RPMSG GET/SET FLOWCONTROL IOCTL support") Cc: stable@vger.kernel.org Signed-off-by: Yu Zhang --- v2: - Drop the paragraph about the other ept_lock users from the commit message (Mathieu). - Bail out early when the endpoint is already gone instead of an if/else around the call (Mathieu). v1: https://lore.kernel.org/all/20261026100306.68019-1-yuz08559@gmail.com/ --- drivers/rpmsg/rpmsg_char.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c index 550fda2..d8868fa 100644 --- a/drivers/rpmsg/rpmsg_char.c +++ b/drivers/rpmsg/rpmsg_char.c @@ -343,7 +343,20 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd, break; } set = !!arg; - ret = rpmsg_set_flow_control(eptdev->ept, set, eptdev->chinfo.dst); + + ret = mutex_lock_interruptible(&eptdev->ept_lock); + if (ret) + break; + + if (!eptdev->ept) { + mutex_unlock(&eptdev->ept_lock); + ret = -EPIPE; + break; + } + + ret = rpmsg_set_flow_control(eptdev->ept, set, + eptdev->chinfo.dst); + mutex_unlock(&eptdev->ept_lock); break; case RPMSG_DESTROY_EPT_IOCTL: /* Don't allow to destroy a default endpoint. */ -- 2.43.0